Automatic balanced weighbeam system



June 22, 1965 J, SORTEBERG 3,190,553

AUTOMATIC BALANCED WEIGHBEAM SYSTEM Filed Aug. 8. 1962 V 3 V i 7? 20 0 z INPUT AIR SUPPLY OUTPUT ,NVENT ATTORNEY United States Patent 3,190,553 AUTOMATIC BALANCED WEIGHBEAM SYSTEM Johannes Sorteberg, 540 Connecticut Ave., Darien, Conn. Filed Aug. 8, 1962, Ser. No. 215,658

2 Claims. (Cl. 235200) the above equation has been solved to a considerable v degree of accuracy.

For the purpose of illustrating the invention, I have shown in the accompanying drawings a preferred embodiment of it which I have found in practice to give satisfactory and reliable results. It is, however, to be understood that the various instrumentalities of which the invention consists can be variouslyarranged and organized, and the invention is not limited, except by the scope of the appended claims, to the exact arrangement and organization of these instrumentalities as herein set forth.

FIGURE 1 is a horizontal sectional view of an automatically balanced weighbeam system showing the principal elements of my invention.

FIGURE 2 is an enlarged sectional view of the weighbeam and certain of its adjuncts.

FIGURE 3 is a section on line 2-2 of FIGURE 2.

Referring to the drawings:

A body portion 1 forming a fixed support has an air motor AM, the base 2 of which is mounted on the body portion. The air motor has a rod 3 mounted in it for linear movement, and its outer end is connected to a cap 4 having a diaphragm 5 within a housing 6 mounted on the base 2. A spring 7 opposes inward movement of the rod 3.

Fulcrum rollers 8 and 9 are confined in a raceway 10 of a cage 11. The raceway 10 permits the lateral movement of the fulcrum rollers and prevents their longitudinal movement relative to the cage.

Two weighbeams 12 and 13 are suspended from the body portion by leaf springs 14 and 15 which are laterally adjustable by levers 16 and 17 and screws 18 and 19. The contact lines between the fulcrum rollers 8 and 9 and the weighbeams become the fulcrums F1 and F2. The fulcrum rollers may be positioned anywhere along the weighbeams.

The rod 3 is guided in a bearing 20 in the air motor case 2, and cage 11 is confined between guide plates 21, 22, 23 and 24. The fulcrum rollers 8 and 9 bridge across the guide plates which absorb the difference, if any, between the forces A plus B and the opposing forces C plus D produced by load cells A, B, C and D which act upon the weighbeams and pairwise on the same center line.

The weighbeams are U shaped in cross section, and are equipped with pins 29,30, 31 and 32 which absorb the thrust of the rods. The contact lines between the rods and pins become the end fulcrums of the weighbeams.

The weighbeams have extensions 37 and 38 which face nozzle blocks NL and NR with nozzles 39 and 40 and restrictions 41 and 42.

The nozzle blocks are mounted on bellows 43 and 44 which in turn are mounted on fixed blocks 45 and 46.

Load cells B, C and D are assumed to be of the same construction as load cell A, but only a load cell connected to a nozzle assembly must be bellows equipped as shown, inputs are to load cells A, B and D.

The back pressure tap of nozzle block NL communicates with auxiliary bellows 43 and is connected to the air Patented June 22, 1965 motor AM through passage 47. The back pressure tap of nozzle block NR communicates with bellows 44 as well as with load cell C through passage 48. This is also the output connection of the instrument.

In normal operation forces represented by A, B, C and D are exerted on the weighbeams through the medium of bellows. Forces A, B and D may be transmitted to the weighbeams through other media such as springs, magnets, etc. When the system is in balance it is evident that the moments of forces A, B, C and D around fulcrums F1 and F2 present the following equations:

A.w=B.b C .b=D.a

by multiplication we arrive at the equation:

A.C.a.b=B.D.a.b

This equation does not consider two sources of error which for most practical purposes are negligible. However for extremely accurate measurements these errors should be considered. One source of error is the jet effect produced by the detector nozzles facing the weighbeams. This is not dealt with in this application but is covered in a copending application. The other source of error is the slight movement of the weighbeams in relation to the nozzles which is necessary in order to produce variable back pressures for the automatic balancing of the system. The reason why these slight movements heretofore caused errors is that it is impossible to make perfect load cells i.e. make them operate like perfect pistons. The bellows have spring effect and the nozzles were stationary. Therefore, a slight change of force is required in order to move the pushrods which in turn move the weighbeams relative to the nozzles. This invention provides means for eliminating the movement of the bellows by moving the nozzles instead of the bellows so as to maintain the weighbeams stationary.

Let us first consider weighbeam 12. Air is introduced to load cell A, this will create a back pressure from nozzle 39 which is transmitted to the air motor AM, this back pressure is also transmitted to the auxiliary bellows 43 which in turn carries detector nozzle 39. The characteristics of the auxiliary bellows is such that the nozzle moves toward or away from the weighbeam the exact amount required to keep the weighbeam stationary when the pressure is varied on the air motor. This may be further explained as follows: Assume that it requires a relative movement of .003" between the nozzle and the weighbeam to produce say 0l5# back pressure which we will assume is also therequired amount of pressure change necessary on the air motor in order to move the fulcrums from one end of the weighbeam to the other end. This pressure is connected to the auxiliary bellows 43 which is characterized in such a manner as to move the nozzle 0.003 in a linear manner when the pressure varies from 0-15#. We also assume linear characteristics of the air motor. Thus the nozzle moves the proper amount to keep the weighbeam stationary as the fulcrum moves.

Consider next the second weighbeam 13. Here the back pressure from the nozzle is transmitted to load cell C but at the same time also connected to auxiliary bellows 44 carrying the nozzle 40 and positioning same in relation to the weighbeams so as to make the latter stationary when the pressure is varied on load cell D.

As in the case of auxiliary bellows 43, bellows 44 is also assumed linear, i.e., it will expand in direct proportion to its internal pressure, say .003" for 015# pressure change.

Also, as before, the back pressure from nozzle 40 is I 3 assumed to be linear i. e., in direct proportion to its distance from the weighbcam or baffle.

It is evident that regardless of the input pressure D and the position of the movable fulcrumit is necessary to have a movement of the nozzle in relation to the weighbeam in order to create the back pressure C to satisfy the moment formula D.a=C.b. However, it is immaterial in this respect whether the movable element is the Weighbeam or the nozzle. In order to maintain the Weighbeam stationary when the moments are balanced, I have chosen to make the nozzle movable. Thus, by choosing the proper characteristics of the auxiliary bellows which is carrying the nozzle and subjected to the back pressure C, the weighbeam will remain stationary in its balanced position.

Having thus described my invention what I claim and desire to secure by Letters Patent is:

1. A weighbeam system, comprising a weighbeam, end fulcrum points for said weighbeam, a fixed supporting structure for said weighbeam, and movable fulcrum means for said weighbeam, means for applying a force to each end fulcrum point of said weighbeam, means for balancing the moments on said weighbeam by movement of said movable fulcrum means, and means for keeping the weighbeam in all balanced positions in the same fixed position in relation to the supporting structure.

2. A weighbeam system, comprising a weighbeam, end fulcrum points for said weighbeam, a fixed supporting structure for said weighbearn, and movable fulcrum means for said weighbeam, means for applying a force to each end fulcrum point of said weighbcam, means for balancing the moments on said Weighbeam by changing the force applied to one of the end fulcrum points of said Weighbeam, and means for keeping the weighbeam in all balanced positions in the same fixed position in relation to the supporting structure.

5 i References Cited by the Examiner UNITED STATES PATENTS 2,643,055 6/53 Sorteberg 235-61 2,743,735

5/56 Du Bois 137-85 

1. A WEIGHBEAM SYSTEM, COMPRISING A WEIGHBEAM, END FULCRUM POINTS FOR SAID WEIGHBEAM, A FIXED SUPPORTING STRUCTURE FOR SAID WEIGHBEAM, AND MOVABLE FULCRUM MEANS FOR SAID WEIGHBEAM, MEANS FOR APPLYING A FORCE TO EACH END FULCRUM POINT OF SAID WEIGHBEAM, MEANS FOR BALANCING THE MOMENTS ON SAID WEIGHBEAM BY MOVEMENT OF SAID MOVABLE FULCRUM MEANS, AND MEANS FOR KEEPING 